Nice job, it help me to confirm the assumptions!
I agree, I have understood the same thing about the difference with/without memory. If you look into the heated seat retrofit document, they connect all the wiring regardless if you have the memory or not. So I think itís safer to add the K_CAN but keeping all the legacy wires as described.
For the other pins #6 & #7, they could be unused on the E90 but used on other cars. Itís like the memory module, there is an empty slot. Do you know if BMW is offering other seat options on other models?